Certification Process | WiMAX Certifications

The WiMAX certification process is the steps, processes and tests which are performed to ensure that products will perform as desired and will reliably interoperate with other devices that are certified.

Testing for WiMAX products can be performed using testing conformance standards. The WiMAX test standards include a protocol implementation conformance statement (PICS), a test suite structure (TSS) and a radio conformance testing (RCT).

A protocol implementation conformance statement proforma is a document that is provided by a company or testing facility that states that the product or system provides and supports a specific set of commands and protocols. The 802.16 system has many capabilities and WiMAX devices typically are designed to support only a limited set of the protocols and capabilities.

A test suite structure (TSS) is a set of testing equipment configurations and procedures that are used to evaluate the operation and performance of products or systems. For the WiMAX system, the TSS performs operational testing of key functions of WiMAX devices including connecting radio links, authenticating, setting up, and changing services.

Radio conformance tests are a set of procedures that are used to evaluate the operation and performance of the radio part of wireless products or systems.

Service Flows and Classes

WiMAX services are the providing of information transfer to or between users. Information transfer services can have a variety of characteristics that can be selected and varied by the operator. The WiMAX system uses services flows to identify specific transmission characteristics for specific user services and a single user may have multiple service flows. Common sets of service characteristics may be defined by service classes.

Service Flows

Service flows are communication channels (e.g. a stream of packets) that have particular service characteristics associated with the transfer of data. For example, a communication link might have several service flows associated with it; a real time service flow for voice communication, a high-integrity service flow (low error rate) for data file transfer and a best effort service flow for Internet web browsing.

Each service provided on a WiMAX system is associated with a service flow. Service flows are requested, established and ended. When subscriber stations request services, the system can evaluate and negotiate the requested characteristics at any time.

A single WiMAX subscriber station may have multiple service flows for each connection (service flows can be different in different directions). Service flows can be dynamically added, changed and ended.

Service flows are uniquely identified by a service flow identifier (SFID). A SFID is associated with a specific connection identifier to determine the service characteristics a specific user will receive on that particular device

Unsolicited Grant Service (UGS)

Unsolicited grant service is a service flow in which the transmission system automatically and periodically provides a defined number of timeslots and fixed packet size that is used by a particular receiver. UGS is commonly used to provide services that require a constant bit rate (CBR) such as audio streaming or leased line (e.g. T1 or E1) circuit emulation.

UGS provides a constant bit rate for a single connection. A subscriber device may need additional bandwidth for an additional service that is added to a connection or to temporarily provide more bandwidth on the UGS connection. To request more bandwidth on a UGS connection, a poll me bit or slip indicator bit may be used.

A poll me bit is a signaling message in a data field within the header of a data packet that indicates that the device would like to be polled. The poll me bit indicates to the base station that the subscriber device needs to be polled for a service other than for the current UGS service.

For transmission to synchronous connections, timing inaccuracies may result in the need to transfer additional bits if the clock of one connection is slightly faster than the other connection. When the buffer of the faster connection indicates the number of bits to be transmitted may soon run out, a slip indicator bit may be used. The slip indicator is a signaling message within the header of a data packet that indicates that the data transmission queue of that device is changing (slipping) and that the device needs more bandwidth to keep up with the transmission queue. This allows the base station to temporarily assign additional bandwidth until the transmission buffer has caught up.

Figure 1 shows how WiMAX unsolicited grant service (UGS) operates. Subscriber stations are assigned to receive and transmit during assigned time intervals. The subscriber station may use the poll me bit in the header to indicate it wants to be polled so it can send data for another service. When the base station receives the poll me bit, it sends a polling message which allows the subscriber station to send a packet of data that is independent of the UGS packets.

Figure 1: Wireless Unsolicited Grant Service (UGS)